This is a Congressionally mandated study to determine whether the children exposed to chloride deficient formula in 1978 and 1979 may have suffered some long-term effects which may be expressed in delayed motor and mental development or decreased school performance. The activity of the past year has centered on 1) identifying subjects eligible for study as cases, 2) investigating the potential problems exposed children may have, 3) defining the test battery that cases and controls will undergo, 4) a pilot test of all study procedures, 5) a pilot test of a complete battery of potentially useful neuropsychological tests, and 6) the completion of a population-based study of children exposed to chloride deficient formula and their appropriate controls. Case finding has consisted of surveys of pediatric nephrologists, pediatricians in several states and a systematic CPHA search. Problem identification has consisted of the careful review of several hundred potential case records, a literature review, discussion with physicians who have treated cases, and a review of problems as described by parents.